/*
    Copyright (c) 2011, Daniel Guerrero
    All rights reserved.

    Redistribution and use in source and binary forms, with or without
    modification, are permitted provided that the following conditions are met:
        * Redistributions of source code must retain the above copyright
          notice, this list of conditions and the following disclaimer.
        * Redistributions in binary form must reproduce the above copyright
          notice, this list of conditions and the following disclaimer in the
          documentation and/or other materials provided with the distribution.

    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
    ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
    WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
    DISCLAIMED. IN NO EVENT SHALL DANIEL GUERRERO BE LIABLE FOR ANY
    DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
    (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
    LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
    ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
    (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
    SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

(function(exports) {

    var keyStr = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=';

    exports.decode = function(input) {
        // get last chars to see if are valid
        var lkey1 = keyStr.indexOf(input.charAt(input.length - 1));
        var lkey2 = keyStr.indexOf(input.charAt(input.length - 2));

        var bytes = (input.length / 4) * 3;
        if (lkey1 == 64) bytes--; // padding chars, so skip
        if (lkey2 == 64) bytes--; // padding chars, so skip

        var uarray;
        var chr1, chr2, chr3;
        var enc1, enc2, enc3, enc4;
        var i = 0;
        var j = 0;
        uarray = new Uint8Array(bytes);

        input = input.replace(/[^A-Za-z0-9\+\/\=]/g, '');

        for (i = 0; i < bytes; i += 3) {
            // get the 3 octects in 4 ascii chars
            enc1 = keyStr.indexOf(input.charAt(j++));
            enc2 = keyStr.indexOf(input.charAt(j++));
            enc3 = keyStr.indexOf(input.charAt(j++));
            enc4 = keyStr.indexOf(input.charAt(j++));

            chr1 = (enc1 << 2) | (enc2 >> 4);
            chr2 = ((enc2 & 15) << 4) | (enc3 >> 2);
            chr3 = ((enc3 & 3) << 6) | enc4;

            uarray[i] = chr1;
            if (enc3 != 64) uarray[i + 1] = chr2;
            if (enc4 != 64) uarray[i + 2] = chr3;
        }

        return uarray;
    };

})(module.exports);